Add examples for important functions/types

[samlaf]

See https://go.dev/blog/examples

examples show up in godoc so will be very useful for helping avs teams understand our modules.

[samlaf]

Added the first example here. We should add more for the core functionalities as well. This is way better than having outdated code in READMEs because these godoc examples are forced to compile, so we have to update them when interfaces or structs change.